IC device authentication using energy characterization

ABSTRACT

Systems, methods, and apparatuses are described for verifying the authenticity of an integrated circuit device. An integrated test apparatus may use quiescent current and/or conducted electromagnetic interference readings to determine if a device under test matches the characteristics of an authenticated device. Deviations from the characteristics of the authenticated device may be indicative of a counterfeit device.

This application is a continuation of and claims priority to co-pendingU.S. application Ser. No. 16/870,221 filed May 8, 2020, and entitled “ICDevice Authentication Using Energy Characterization,” which claimspriority to U.S. application Ser. No. 16/713,413 filed Dec. 13, 2019,which issued as U.S. Pat. No. 10,684,324 on Jun. 16, 2020, and entitled“IC Device Authentication Using Energy Characterization,” which claimspriority to U.S. application Ser. No. 16/275,612 filed Feb. 14, 2019,which issued as U.S. Pat. No. 10,585,139 on Mar. 10, 2020, and entitled“IC Device Authentication Using Energy Characterization,” which isincorporated herein by reference in its entirety.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support under Contract“Counterfeit Electronics Avoidance and Detection, DOTC-16-01 INIT0950”awarded by the Defense Ordnance Technology Consortium. The governmenthas certain rights in the invention.

BACKGROUND

Sourced components may be required to conform to particularspecifications or match certain architectures. A manufacturer mayspecify particular makes and models of integrated circuit devices to beused in a product. However, part suppliers may intentionally orunintentionally provide devices that may partially conform torequirements, but that may be defective or a fraudulent (e.g.,counterfeit) device. In some instances, counterfeit devices maygenerally mimic the behavior of the devices they copy, even though theymay have a reduced reliability, reduced operational life and/or otherdrawbacks.

SUMMARY

This Summary is provided to introduce a selection of several exemplaryconcepts in a simplified form as a prelude to the Detailed Description.This Summary is not intended to identify key or essential features.

An integrated test apparatus may determine whether an unauthenticatedintegrated circuit device conforms to expected standards (e.g.,determine if the device is of the make, model, and/or manufacturerexpected). The integrated test apparatus may measure a quiescent currentproduced by the device under test, at multiple voltage steps, andwithout a load. The quiescent current measurements may be compared tomeasurements from an authenticated device for authentication. Theintegrated test apparatus may also or alternatively determine conductedelectromagnetic interference produced by the unauthenticated deviceunder test at load. The conducted electromagnetic interference may becompared to measurements from an authenticated device forauthentication. The integrated test apparatus may indicate whether anunauthenticated device meets requirements (or, e.g., whether it iscounterfeit) based on the results of the one or more comparisons tomeasurements of the authenticated device.

These and other features are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Some features are shown by way of example, and not by way of limitation,in the figures of the accompanying drawings and in which like referencenumerals refer to similar elements.

FIG. 1 shows an example integrated test apparatus for integrated circuitverification and testing.

FIG. 2 shows an example of a conducted electromagnetic interferencemeasurement system.

FIG. 3 shows an example of an excitation circuit and an electromagneticinterference energy calculation circuit.

FIG. 4 shows an example system for performing integrated circuitverification using QC detection and analysis.

FIG. 5 shows an example of a quiescent current measurement circuit.

FIG. 6 shows an example of an integrated testing curve.

FIG. 7 shows an example method for integrated quiescent current andconducted electromagnetic interference testing.

DETAILED DESCRIPTION

Integrated circuit (IC) devices may have measurable characteristics thatare consistent for a given implementation of a device. An implementationof a device may comprise a particular architectural design asmanufactured by a particular entity. Even slight variations, such as theuse of different sub-components, materials, or architectural variations,may produce different characteristics, affect reliability, and/or affectan operation lifetime of the device.

A given implementation of an IC device may have particularelectromagnetic interference (EMI) characteristics. EMI characteristicsmay comprise a pattern of electromagnetic emissions produced by an ICdevice under a static and/or dynamic load. For example, an IC device mayproduce a unique EMI signature under a static voltage and/or when givena particular series of inputs (e.g., a stepped voltage, digital inputsin a sequence, etc.). EMI may comprise detectable electromagneticemissions, such as conducted EMI and/or radio-frequency emissions. EMImay also comprise disturbances on a power flowing from a power source tothe IC device. For example, conducted EMI may comprise high frequencydisturbances that are present on a connection to a positive terminal(e.g., power input) of an IC device.

A given implementation of an IC device may have particular quiescentcurrent (QC) characteristics. QC characteristics may comprise currentdraw on one or more power inputs and/or outputs of an IC device, such aswhen the IC device has no load and/or when the IC device is receiving nosubstantive inputs (e.g., no analog or digital inputs and/or operatingin an idle state). For example, an IC device may produce a unique QCsignature under steady-state power with no other inputs. This may be theresult of internal characteristics of the IC (e.g., the architecture,capacitance, resistance, inductance, etc.). QC current may be detectableat the one or more power inputs of the IC as an in-line currentmeasurement.

Testing for EMI and/or QC characteristics may provide a reliable andefficient method for determining the authenticity of an unauthenticateddevice (e.g., determining whether an unauthenticated IC device conformsto required specifications and/or is of the manufacturer, make, and/ormodel listed). By comparing the EMI and/or QC characteristics of theunauthenticated IC device to those of an authenticated IC device (e.g.,a known, conforming IC device), the authenticity of an unauthenticatedIC under test may be determined.

FIG. 1 shows an example integrated test apparatus for IC deviceverification and testing. This example may provide both QC and conductedEMI capabilities. The integrated test apparatus 100 may comprise one ormore components that may work in conjunction to verify that an IC deviceconforms to required specifications (e.g., that it is the requested makeand model from a given manufacturer). An IC device under test (DUT)interface circuit 110 may provide an interface to an unauthenticated ICdevice undergoing testing (e.g., a DUT). For example, the DUT interfacecircuit 110 may comprise a socket into which the DUT may be inserted.The DUT interface circuit 110 may be connected to one or more othercomponents of the integrated test apparatus 100 such that the DUTinserted into the DUT interface circuit 110 is electrically connected tothe one or more other components of the integrated test apparatus 100.

The integrated test apparatus 100 may comprise one or more componentsthat may be connected to power inputs of the DUT interface circuit 110.For example, power inputs for an IC device socket of the DUT interfacecircuit 110 may be connected to one or more of a digital to analogconverter power circuit 120, an excitation circuit 130, or amicrocontroller 160. The digital to analog converter (DAC) power circuit120 may comprise a DAC power circuit configured to generate a directcurrent (DC) voltage source. The DAC power circuit 120 may derive adirect current voltage from an alternating current input power source(e.g., a wall socket). The DAC power circuit 120 may be configured toallow for multiple voltages, which may step up in voltage over time. Forexample, the DAC power circuit 120 may provide 1V at a first time, 2V ata second time, 2 V at a second time, . . . 11V at an eleventh time, andthen 12V as a steady-state voltage afterwards. FIG. 6 provides anexample of such or similar operation.

The excitation circuit 130 may provide an input to the DUT to exciteconducted EMI on the power inputs of the DUT. For example, theexcitation circuit 130 may provide an oscillating analog or digitalinput to the DUT interface circuit 110, which may be configured toprovide that oscillating analog or digital input to the DUT.

The microcontroller 160 may control one or more aspects of theintegrated test apparatus 100. The microcontroller may control generaloperation of the integrated test apparatus 100, such as by turning on apower supply or switching on an input. For example, the microcontroller160 may control the excitation circuit 130 generating an excitationinput to the DUT.

The integrated test apparatus 100 may comprise one or more componentsthat may measure signals via connections to the DUT interface circuit110. A QC compression amplifier circuit 140 may be connected to the DUTinterface circuit 110 to detect QC draw from the DUT. For example, theQC compression amplifier circuit 140 may be connected to power inputs to(or outputs from) the DUT interface circuit 110 (e.g., in-line from theDAC power circuit 120). The QC compression amplifier circuit 140 maygenerate a compressed reading of QC generated by an excited DUT formeasurement by the microcontroller 160.

An energy calculation circuit 150 may be configured to read EMIcharacteristics of the DUT (e.g., conducted EMI on the power inputs ofthe DUT). For example, the energy calculation circuit 150 may beconfigured to read conducted EMI on a connection between a DAC powercircuit 120 and the DUT interface circuit 110. The energy calculationcircuit 150 may transmit those readings to the microcontroller 160 forfurther processing and/or reporting.

FIG. 2 shows an example of a conducted EMI measurement system 200. TheEMI measurement system 200 may comprise one or more components of theintegrated test apparatus 100. The EMI measurement system 200 may detectconducted EMI for a DUT 270 using a power supply 205, an excitationsource 260, and/or a load 255. The DUT 270 may be a DUT in the DUTinterface circuit 110.

The power supply 205 may comprise a voltage source. The power supply 205may be a DAC power circuit 120. The power supply 205 may provide a powersupply current 210 to a DUT 270. The DUT 270 may be provided an inputfrom an excitation source 260 which may comprise an excitation waveform265. The DUT 270 may drive a load 255 (e.g., a linear resistor). The DUT270 may feed return current 275 to the power supply 205. In someinstances, the current direction may be reversed from that shown in FIG.2 (e.g., current may be depicted as the flow of electrons, which may beopposite to the current flow depicted).

The power supply current 210 may comprise power fluctuations (e.g.,conducted EMI induced by the excitation waveform 265 to the DUT 270).One or more devices 215 capable of conducted EMI measurement may beconnected (e.g., in-line, which may refer to a connection in seriesbetween the power supply 205 and the DUT 270) to the positive voltagelead for the DUT 270. One device may be oscilloscope 220, which mayproduce a time graph 235 which may display the conducted EMI on thepositive supply voltage source as a function of time. Another device maybe a spectrum analyzer 225, which may provide a frequency graph 240which displays various frequency components of the EMI conducted on thepositive supply voltage input to the DUT 270. These may be displayed toa user and/or may be fed to a device (e.g., the microcontroller 160) foradditional computations 245. The additional computations 245 may, forexample, comprise comparisons of graphed results with those of known(e.g., baseline) devices. The additional computations 245 may be used togenerate other outputs, such as human-readable outputs.

Energy calculator 230 may be a circuit and/or computational device whichmay produce human-readable output 250. The human-readable output 250 maybe a simple output, such as a number or indicator that is representativeof the energy associated with the conducted EMI (e.g., “133”). A readingwithin a given range may be indicative of a verified DUT. The energycalculator 230 may be configured to compare the conducted EMI of the DUT270 with the conducted EMI of an authenticated device. Thehuman-readable output 250 may comprise an indication of variance (e.g.,an r-squared value) or a simple yes/no output (e.g., a red light glowingfor a successful test).

The conducted EMI may be characterized in the time domain (with anoscilloscope-like capability) and/or in the frequency domain (with aspectrum analyzer-like capability). The analyses in the time and/orfrequency domain may be equally effective. However, a disadvantage ofboth is that relatively high-level instrumentation (either anoscilloscope or spectrum analyzer) may be required for the measurement,initial processing, and recording of the EMI data. In addition,comparing the results of time domain or frequency domain informationwith those of authenticated devices may require significant additionalpost-processing capabilities. As such, these conducted EMImeasurement/analysis approaches may complicate the overall hardware andprocesses for an IC device authentication system. The approach of usingan analog energy calculation circuit (e.g., the energy calculator 230)for the characterization of the conducted EMI significantly may simplifythe authentication hardware and process. The analog calculation circuitmay generate a single scaler value which can be compared directly withthat of an authenticated device, therefore facilitating anauthentication system that may be simpler, smaller, and less expensive.

FIG. 3 shows an example of an excitation circuit 300 and an EMI energycalculation circuit 305. The excitation circuit 300 may be theexcitation circuit 130. The EMI energy calculation circuit 305 may be animplementation of the energy calculator 230. The excitation circuit 300may provide power and input signals to a DUT 325. The DUT 325 may be aDUT in the DUT interface circuit 110. The EMI energy calculation circuit305 may be connected to the power signals (e.g., via a high-pass filter315) in order to read a conducted EMI signal. The output of the EMIenergy calculation circuit 305 may be fed to a microcontroller 355,which may analyze the conducted EMI characteristics, and display thosecharacteristics (or an analysis of those characteristics, such as howthe characteristics correspond to an authenticated IC) on a display 350.The microcontroller 355 may also facilitate storage of test data and/orcommunication of test data to a higher-level information system. Thedisplay 350 may display the results of a test and any other pertinentinformation (e.g., the device type that is being tested, date and time)that may be related to the test.

The excitation circuit 300 may comprise a power supply 310 that feedsdirect current power to a high pass filter 315. The excitation circuit300 may be the excitation circuit 130. The power supply 310 may be theDAC converter power circuit 120. The high pass filter 315 (which may bea crossover filter) may pass the direct current from the power supply310 to the DUT 325. The DUT 325 may receive an input from an excitationsource 320. The input may comprise an oscillating waveform input (e.g.,operating at one of several possible frequencies at 1 Mhz, 10 Mhz, 10Khz, etc.). The excitation source 320 may be crystal-controlled. Theexcitation output may be a square wave signal (e.g., a square wave at5V). The excitation source 320 may be connected via buffer circuits,which may prevent input loading characteristics of the DUT 325 fromaffecting the operating characteristics of the excitation source 320.The DUT 325 may also drive a load 330. The microcontroller 355 maycontrol or provide the excitation source 320. For example, themicrocontroller 355 may be configured (e.g., preconfigured, orcontrolled using a user interface) to control the excitation source 320(e.g., instruct an excitation device to operate as the excitation source320 at an instructed frequency or time) or may provide the excitationsource 320 via an output of the microcontroller 355.

The high pass filter 315 may comprise a filter which extracts highfrequency signals associated with the conducted EMI conducted on thepower input to DUT 325. The high pass filter 315 may redirect thosecomponents (e.g., high frequency signals) to the EMI energy calculationcircuit 305 to the input of pre-amplifier 335. The EMI energycalculation circuit 305 may be the energy calculation circuit 150. Thepre-amplifier 335 may amplify the high frequency components (e.g., witha gain of 3.8 and a bandwidth of at least 150 Mhz), and provide theamplified high frequency components to a wideband analog multiplier 340.The wideband analog multiplier 340 may apply a squaring operation to theamplified high frequency components, and may be followed by a lossyintegrator 345. Both inputs to the wideband analog multiplier 340 may beamplified conducted EMI signals. Both inputs may be the same signal. Theoutput of the wideband analog multiplier 340 may be proportional to thesquare of the conducted EMI signal.

One or more amplified conducted EMI signals may be represented as aseries of cosine and sine functions:

${V_{EMI}(t)} = {\sum\limits_{n = 1}^{\infty}\left( {{a_{n} \cdot {\cos\left( {2\pi{nf}_{o}t} \right)}} + {b_{n} \cdot {\sin\left( {2\pi{nf}_{o}t} \right)}}} \right.}$

where f_(o)=the fundamental frequency of the excitation waveform.Squaring V_(EMI)(t) may yield:

${V_{EMI}^{2}(t)} = \left\{ {\sum\limits_{n = 1}^{\infty}\left( {{a_{n} \cdot {\cos\left( {2\pi{nf}_{o}t} \right)}} + {b_{n} \cdot {\sin\left( {2\pi{nf}_{o}t} \right)}}} \right)} \right\}^{2}$

The squaring operation may result in squares of like terms, such as:(a ₂·cos(4πf _(o) t))²+(a ₄·cos(8πf _(o) t))²+(a ₆·cos(12πf _(o) t))²+ .. .(b ₁·cos(2πf _(o) t))²+(b ₃·cos(6πf _(o) t))²+(b ₅·cos(10πf _(o) t))²+ .. .

For each square of like terms, the results may be simplified using theappropriate trigonometric identity as follows:

${a_{n}^{2} \cdot \left( {\cos\left( {2\pi{nf}_{o}t} \right)} \right)^{2}} = {\frac{a_{n}^{2}}{2} + {\frac{a_{n}^{2}}{2} \cdot {\cos\left( {4\pi{nf}_{o}t} \right)}}}$${b_{n}^{2} \cdot \left( {\sin\left( {2\pi{nf}_{o}t} \right)} \right)^{2}} = {\frac{b_{n}^{2}}{2} - {\frac{b_{n}^{2}}{2} \cdot {\cos\left( {4\pi{nf}_{o}t} \right)}}}$

Therefore, the square of each like term at the output of the widebandanalog multiplier 340 may produce a constant time invariant term (a “DCterm”). Furthermore, these DC terms may be additive across the entireseries and may represent the square of the EMI signal. Therefore, thetotal DC signal at the output of the multiplier circuit may be aresultant waveform given by:

$V_{DC} = {{\frac{1}{2} \cdot {\sum\limits_{n = 1}^{\infty}a_{n}^{2}}} + b_{n}^{2}}$

This signal may be proportional to the total energy associated with theconducted EMI signal and may be used as a marker for thecharacterization of the conducted EMI. This signal may appear at theoutput of the wideband analog multiplier 340 in the midst of the othertime-varying products that are produced as a result of the squaringoperation. Therefore, it may be advantageous to filter the time-varyingcomponents to provide for an accurate reading of the direct currentvoltage for the characterization of the conducted EMI.

The lossy integrator 345 may process the input received from thewideband analog multiplier 340, and transmit a resultant reading to themicrocontroller 355. The lossy integrator 345 may filter the DCcomponent from the output of the analog multiplier circuit. The lossyintegrator 345 may provide a relatively short charging time (e.g., ˜10us) with a much longer discharge time (e.g., ˜330 us). This combinationof charge/discharge times may provide an approximated average of theoutput of the multiplier circuit. As such, the lossy integrator mayprovide a clean direct current output level voltage which can be readwith a multi-meter or posted on the display 350 via the microcontroller355. The lossy integrator 345 may also provide additional gain so as toincrease the span and resolution of the direct current signal level.Thus, the EMI energy calculation circuit 305 may process the conductedEMI signal by using the wideband analog multiplier 340 and the lossyintegrator 345 to produce a single direct current voltage that is arepresentation of the energy (e.g., the total energy across thespectrum) of the conducted EMI signal.

FIG. 4 shows an example system for performing IC device authenticationusing QC detection and analysis. An IC device Interface 400, which maybe a DUT interface circuit 110, may provide a connection to a DUT 405. AQC measurement circuit 410, which may comprise a QC compressionamplifier circuit 140, may measure QC generated by the DUT 405. Acomputational platform 415 may collect the QC data and perform thenecessary comparative analysis and decision processes to determine ifthe DUT 405 meets requirements. The computational platform 415 maycomprise one or more computer processors and memory, performing one ormore methods described herein (e.g., performing steps 745, 755, and 760of FIG. 7 ). The IC device interface 400 facilitates electricalconnections between pins of the DUT 405 to the QC measurement circuit410. The IC device interface 400 may use commercially available testsockets that enable the DUT 405 to be easily and quickly inserted andextracted without any damage to leads of the DUT 405. QCcharacterization may, in at least some examples, only require electricalconnections to the power supply leads of the DUT 405. This may involveconnecting to two leads of the DUT 405 (e.g., +Vcc and GND). The ICdevice leads connected to the QC measurement circuit 410 may be adjustedmanually or automatically (e.g., upon instruction from amicrocontroller). The QC measurement circuit 410 may provide a result tothe computational platform 415. The computational platform 415 mayperform data logging, comparative analysis, and/or decision making todetermine if the DUT 405 meets requirements. An indication of whether aDUT 405 meets requirements (e.g., if an IC device is or is notcounterfeit) may be made using an indicator such as a potentialcounterfeit indication 420. The potential counterfeit indication 420 maybe a user-readable output, such as a light (e.g., red for failure and/orgreen for passing), a terminal output (e.g., the word “failure”displayed on a terminal), or any other indication suitable to indicate atest failure to a user.

FIG. 5 shows an example of a QC measurement circuit 500. The QCmeasurement circuit 500 may comprise one or more components of theintegrated test apparatus 100. The QC measurement circuit 500 mayprovide an excitation voltage to a DUT and facilitate measurement andcharacterization of the quiescent current flowing through the DUT. Anexcitation voltage, which may increase over a number of incrementalsteps, may be provided by a digital-to-analog converter (DAC) 510. Amicrocontroller 505, which may be a microcontroller 160, may control theDAC 510. The microcontroller may send a communication (e.g., a 6-bitbinary word) to the DAC 510, which may produce a voltage ramp at itsoutput (e.g., a voltage ramp having 64 discrete steps). Command wordsmay comprise any number of bits in order to achieve the desiredexcitation voltage accuracy. The DAC 510 may be augmented byincorporating a voltage amplifier which drives a transistor-basedemitter-follower (a “voltage-follower”). The voltage amplifier may allowthe overall excitation voltage span to be determined independently fromthe DAC 510 circuitry. The overall span of the excitation voltage may beadjusted (e.g., from 0-15 VDC) depending on the gain of the voltageamplifier. The voltage amplifier may drive the voltage-follower whichmay isolate the load impedance of the DUT 520 from the voltageamplifier. This may enable the circuit to provide a wide range ofcurrents to various IC device types without affecting the level of theexcitation voltage.

The output of the DAC 510 may provide a positive excitation voltage tothe +Vcc lead of the DUT 520 through the IC device interface 515. The ICdevice interface 515 may be a DUT interface circuit 110. Current fromthe voltage-follower may be conducted through the DUT 520 and returned,from the GND lead through the IC device interface 515, to the input ofthe compression amplifier 525. The return current may flow through acurrent-viewing-resistor (CVR) which may produce a voltage that isproportional to the QC that is returned from the DUT 520. This resultingvoltage may be used to characterize the QC flowing through the DUT 520as a function of the excitation voltage. Since the QC can range overseveral orders-of-magnitude, both with reference to the changingexcitation voltage and/or the variety of IC devices that may be tested,the voltage from the CVR may be processed through the compressionamplifier 525. The compression amplifier 525 may have a non-linear gain(e.g., providing more voltage gain to smaller input voltage signals andless gain to larger input voltage signals). This may enable therecording of the QC over a wide range without the need to manuallychange amplification factors. The gain characteristics (gain versusinput voltage) of the compression amplifier may be characterized andused in the computational processes to characterize the QC of the DUT520 as a function of the excitation voltage.

As a DUT 520 is being tested, the microcontroller 505 may increment thecommand word to the digital-to-analog converter. This results in anincreasing excitation voltage applied to the DUT 520 that incrementsbased on the command word. In an example for a 6-bit configuration (64steps), the excitation voltage may increment in 63 steps from zero tothe maximum voltage level over a total period of 15-60 seconds. Both theexcitation voltage level and the compressed QC value may be read back tothe microcontroller 505. The microcontroller 505 may store theexcitation voltage/QC values as an internal array or communicate thesevalues to an another computational platform (e.g., externalcomputational platform 540 or internal computational platform 530). Theexternal computational platform 540 and/or internal computationalplatform 530 may comprise one or more computer processors and memory,performing one or more methods described herein (e.g., performing steps745, 755, and 760 of FIG. 7 ). The excitation voltage/QC data may besubsequently subjected to a comparative analysis to determine if the DUT520 meets requirements (or potentially could be a counterfeit device).The computational platforms may produce an indication of the result(e.g., potential counterfeit indication 545 or potential counterfeitindication 535). The potential counterfeit indication 545 and/orpotential counterfeit indication 535 may be a user-readable output, suchas a light (e.g., red for failure and/or green for passing), a terminaloutput (e.g., the word “failure” displayed on a terminal), or any otherindication suitable to indicate test results to a user.

Several techniques may be used to quantitatively compare measured QC andconducted EMI characteristics from a DUT 520 with authenticatedcharacteristics of an authenticated device. The baseline QC andconducted EMI characteristics (which may be displayed using a curve) maybe obtained by performing QC and/or conducted EMI testing (e.g., usingthe systems and methods described herein) on a device known to begenuine (e.g., a device sent by the manufacturer as a sample fortesting). These may include correlation analysis or statistical analysis(e.g., Z-score or variance analysis). These results may be used to gaugethe overall variance of the data regarding a device under test with thebaseline on a point-by-point basis. Relatively small variances from theQC and conducted EMI baseline may be indicative that the DUT 520 isauthentic. Larger variances with reference to the baseline data mayindicate that the DUT 520 may potentially be counterfeit. Someembodiments may automatically compare the measured QC characteristicswith that of the baseline. Some embodiments may automatically determineif the DUT 520 is an authentic device or is seen as potentiallycounterfeit.

FIG. 6 shows an example of an integrated testing curve. An integratedtest apparatus 100 may initially perform a QC test 600 on a DUT, andthen perform a conducted EMI test 605 on the DUT when steady-statevoltage is achieved. The QC test 600 may be performed, wherein thevoltage applied to the power inputs of the DUT may be incrementallystepped from 0 to z (e.g., Vcc). Voltage measurements may be read intoan array 610 with each value corresponding to each step. The integratedtest apparatus 100 may then calculate an r-squared value 630 based onthe measurements stored in array 610 and an authenticated reference IC.If this measurement is outside a tolerance (e.g., 0.001), then acounterfeit device may be indicated. For example, a device with anr-squared of 0.998797 may be genuine, while a device with an r-squaredof 0.874919 may be counterfeit.

After stepping the applied voltage z steps during the QC test 600,steady-state voltage may be achieved. The integrated test apparatus 100may then apply an excitation signal (e.g., 1 MHz) to the DUT (e.g.,according to methods and systems described herein). For example, theexcitation circuit 130 may apply an excitation signal to one or moreinputs of the DUT, and EMI signals from the power circuit may be passedthrough the EMI energy calculation circuit 150 for reading and storageby the microcontroller 160. The integrated test apparatus 100 may readthe EMI voltage as a single EMI value 625. For example, an authenticatedvoltage may be 1.401 volts, and a tolerance may be 10%. In this example,a reading of 1.5 volts may indicate a genuine device, while a reading of1.7 volts may indicate a counterfeit device.

The results 620, which may comprise the r-squared value 630 (e.g., forthe QC measurement) and/or the EMI value 625, may be displayed to a userand/or analyzed for authentication. For example, if one of the r-squaredvalue 630 and/or the EMI value 625 (or a variable computed from both)falls outside an allowable range, the DUT may be identified as failingto meet requirements (e.g., as a counterfeit).

FIG. 7 shows an example method for integrated QC and conducted EMItesting. A test apparatus, such as an integrated test apparatus 100, mayenable the authentication of a DUT. At step 705, the test apparatus maybe configured for testing. The configuration may comprise parameters foroperability with a DUT. For example, a DUT interface circuit 110 may beprogrammed in hardware or software to interface various components(e.g., Vcc, digital/analog inputs, digital/analog outputs, etc.) withconnection to appropriate leads for a given DUT. The configuration maycomprise operating characteristics specific for the device being tested.For example, the test apparatus may be configured to step up voltage ata certain rate and/or to a certain threshold voltage (e.g., 1 V every0.05 seconds until 12 V), and may be configured to run a conducted EMItest at steady state for a certain time (e.g., 0.1 seconds). At step710, a DUT may be inserted into the test socket for testing.

At step 715, the test apparatus may step up voltage for the DUT. Avoltage source may increase a voltage to a point based on aconfiguration (e.g., increase voltage from 1V to 2V). At step 720, thetest apparatus may take a quiescent current reading. For example, thetest apparatus may take a QC reading as described above in FIG. 4 orFIG. 5 . At step 725, the test apparatus may determine if a thresholdvoltage (e.g., Vcc) has been reached. The threshold voltage may be asteady-state voltage (e.g., an operation voltage of the DUT). When thethreshold voltage is reached (e.g., at the steady-state voltage), thetest apparatus may proceed with calculating QC variability (e.g., anr-squared value) at step 730. If the threshold voltage has not beenreached, the test apparatus may continue to incrementally step upvoltage and take readings as in steps 715 and step 720.

At step 730, the test apparatus may calculate QC variability. The QCvariability may be a representation of the current drawn by the DUT ateach step of the voltage test (e.g., compared to an authenticateddevice). The QC variability may be analyzed as a fixed value, or as amatrix of values, such as according to the systems and methods describedherein.

At step 735, the test apparatus may apply an excitation to the DUT. Theexcitation may be a waveform, such as a square wave or an alternatingvoltage, applied to an input of the DUT (e.g., an input other than thepower leads). At step 740, the test apparatus may read one or morevoltages (e.g., VEMI) corresponding to conducted EMI produced on powerleads of the DUT. The conducted EMI may comprise frequency signals thatare imposed upon a direct current power source to the DUT. Furtherdiscussion of conducted EMI may be found, for example, in thediscussions of FIG. 2 and FIG. 3 .

At step 745, the test apparatus may determine if the QC r-squared andconducted EMI readings are within thresholds. Thresholds may be based onknown values corresponding to authenticated devices. Multipleauthenticated devices (e.g., devices supplied by a manufacturer) may betested for tolerances. For example, ten samples may be tested todetermine a range of QC and conducted EMI readings. Thresholds may beset based on those readings, such as setting a threshold range from anyof the tested devices. For example, if a tested range is 1.4 to 1.6volts, a threshold may be set at 10% above and below the tested range(e.g., the threshold for a passing test must be between 1.25 volts and1.75 volts). A DUT meeting thresholds (e.g., within a threshold range)may be authenticated based on having QC and conducted EMIcharacteristics sufficiently similar to an authenticated device in orderto verify that the DUT meets requirements (e.g., is of the same make,model, and/or manufacturer as the authenticated device). A device notsatisfying a threshold may be a device that falls outside a thresholdrange (e.g., a device at 1.1 volts for a range of 1.25 to 1.75 volts).Thresholds may be evaluated based on independent or combined readings.For example, the test apparatus may determine if either of the QCvariability readings or the conducted EMI readings fall outside athreshold. In another example, the test apparatus may calculate acombined value based on both the QC variability reading and the EMIreading, and then evaluate that value against the threshold. Ifthresholds are not met (e.g., if r-squared and/or EMI values are notwithin the threshold), a possible counterfeit device may be indicated atstep 755. For example, a buzzer may sound, a red light may beilluminated, and/or an indication may be made on a display. Ifthresholds are met (e.g., if r-squared and/or EMI values are within thethreshold), then the device may be indicated as acceptable and/or beauthenticated. For example, a chime may sound, a green light may be lit,and/or an indication may be made on a display. In some embodimentsfeedback may only be given for one of a pass or a failure (e.g., analarm may sound for failing to meet a threshold, and no sound may bemade if the DUT readings meet the thresholds).

The foregoing has been presented for purposes of example. The foregoingis not intended to be exhaustive or to limit features to the preciseform disclosed. The examples discussed herein were chosen and describedin order to explain principles and the nature of various examples andtheir practical application to enable one skilled in the art to usethese and other implementations with various modifications as are suitedto the particular use contemplated. The scope of this disclosureencompasses, but is not limited to, any and all combinations,subcombinations, and permutations of structure, operations, and/or otherfeatures described herein and in the accompanying drawing figures.

The invention claimed is:
 1. A method comprising: receiving a firstquiescent current (QC) from a device while the device is subject to afirst voltage; receiving a second QC from the device while the device issubject to a second voltage; determining one or more variability values,comprising one or more r-squared values, based at least in part on: acomparison of the first QC and an expected QC associated with the firstvoltage, and a comparison of the second QC and an expected QC associatedwith the second voltage; and determining, based at least in part on theone or more variability values, that a threshold is not satisfied. 2.The method of claim 1, further comprising applying the first voltageacross a Vcc connection and a GND connection of the device.
 3. Themethod of claim 1, wherein determining the one or more variabilityvalues comprises aggregating: a first difference associated with thecomparison of the first QC and the expected QC associated with the firstvoltage, and a second difference associated with the comparison of thesecond QC and the expected QC associated with the second voltage.
 4. Themethod of claim 1, wherein determining the one or more variabilityvalues comprises: determining, based on the comparison of the first QCand the expected QC associated with the first voltage, a firstvariability value of the one or more variability values; anddetermining, based on the comparison of the second QC and the expectedQC associated with the second voltage, a second variability value of theone or more variability values.
 5. The method of claim 1, furthercomprising: applying, while a direct-current voltage is applied to thedevice, an excitation signal to an input of the device; detecting, basedon the applied direct-current voltage and the applied excitation signal,a tested conducted electromagnetic interference (EMI) value of thedevice; and determining, based on a difference between the testedconducted EMI value and an expected conducted EMI value, that a secondthreshold is not satisfied.
 6. The method of claim 5, further comprisingdetermining that the device is a counterfeit device based on determiningthat both the threshold and the second threshold are not satisfied. 7.The method of claim 1, wherein the one or more r-squared values are anindication of variance.
 8. A method comprising: applying, while adirect-current voltage is applied to a first device, an excitationsignal to an input of the first device; detecting, based on the applieddirect-current voltage and the applied excitation signal, a testedconducted electromagnetic interference (EMI) value of the first devicebased on a high frequency signal on a Vcc connection of the firstdevice; and determining, based on a difference between the testedconducted EMI value and an expected conducted EMI value, that athreshold is not satisfied, wherein the expected conducted EMI value isassociated with a second device.
 9. The method of claim 8, wherein thehigh frequency signal is output from a high pass filter.
 10. The methodof claim 9, wherein detecting the tested conducted EMI value comprisesperforming lossy integration, based on the high frequency signal, todetermine the tested conducted EMI value.
 11. The method of claim 10,wherein detecting the tested conducted EMI value comprises performing asquaring operation, based on the high frequency signal, to determine thetested conducted EMI value.
 12. The method of claim 8, furthercomprising: determining, based on separate applications of a pluralityof different voltages to the first device, a plurality of tested QCvalues; and determining, based on comparing the plurality of tested QCvalues with a plurality of expected QC values associated with the seconddevice, one or more variability values; and determining, based at leastin part on the one or more variability values, that a second thresholdis not satisfied.
 13. The method of claim 12, further comprisingdetermining that the first device is a counterfeit device based ondetermining that both the threshold and the second threshold are notsatisfied.
 14. The method of claim 8, further comprising amplifying thehigh frequency signal.
 15. A method comprising: determining, based onseparate applications of a plurality of different voltages to a firstcircuit, one or more variability values; determining, based on comparingthe one or more variability values with one or more expected values,that a first threshold is not satisfied; determining a tested conductedelectromagnetic interference (EMI) value for the first circuit based onhigh frequency feedback, on a Vcc connection of the first circuit, froman applied excitation signal; and determining, based on a differencebetween the tested conducted EMI value and an expected conducted EMIvalue, that a second threshold is not satisfied.
 16. The method of claim15, wherein determining the tested conducted EMI value comprises:applying a direct-current voltage to the first circuit; applying, whileapplying the direct-current voltage, the excitation signal to an inputof the first circuit; and determining, based on the applieddirect-current voltage and the applied excitation signal, the testedconducted EMI value.
 17. The method of claim 16, wherein determining thetested conducted EMI value comprises performing lossy integration basedon the high frequency feedback.
 18. The method of claim 15, wherein theone or more variability values are responsive to a first voltage acrossthe Vcc connection of the first circuit and a GND connection of thefirst circuit.
 19. The method of claim 15, wherein the one or morevariability values comprise one or more r-squared values, and furthercomprising: determining that the first threshold is not satisfied basedon the one or more r-squared values.
 20. The method of claim 15, furthercomprising amplifying the high frequency feedback.